I am absolutely horrible at grabs. I can do frontside 360s off 10 footers no problem. I also can do some back 1s and switch 1s front and back, but I can't do grabs with any of these. I can do an indy with no spin, but when I try other grabs I lose my balance and start flailing. I know you're supposed to suck up your legs to your body rather than reaching down but for some reason the concept doesn't stick with me. Any advice?

Make sure you generate your torque first, then get stacked over your board. Once your board is directly under you, start tucking like you would in a flip. Tucking helps keep your momentum going throughout the spin. When you are tucked just reach down and try to grab it. Once you are more comfortable with all of this, you can grab most of your spin. But just for now, carry out the motions and just tap for the grab.